A hearing device or hearing aid for an operation in conjunction with a telephone headset to be employed by the user of the hearing aid is known from prior art document US 2006/0013420 A1. This document discloses an arrangement including two hearing aids, one of the hearing aids having means for detecting the presence of a telephone handset close to this hearing aid. Specifically, a sensor is provided for detecting the voice coil of the telephone handset when the handset is held close to the user's ear equipped with the respective hearing aid. When both hearing aids are operated in the normal hearing mode which constitutes a microphone mode for amplifying for the user any noise or sound surrounding the user, and when the particular hearing aid senses the presence of the telephone handset, an automatic switching is performed to an induction receiving mode.
Prior art document US 2005/0175202 A1 discloses a telephone with an integrated hearing aid, wherein both functions are implemented in a single apparatus. When no telephone call is received, the device functions as a normal hearing aid providing the user with amplified sounds of the surrounding sounds. However, when a telephone call is received, the device automatically switches to the function of a telephone and priority is given to the speech information coming from the telephone line. That is, the function of the hearing aid is automatically adapted to receiving and reproducing the telephone call. The function of the hearing aid is not completely switched off, while a telephone call is processed, but the sensing of environmental or surrounding noise is still performed with a higher attenuation. The user can hear both the ongoing telephone call and any noise or sounds surrounding the user.
According to document US 2006/0013420 A1 a switching structure for a hearing aid is known wherein by means of magnetic sensors the presence of a telephone handset is detected. A signal processing circuit of the hearing aid automatically switches the sensitivity to the telephone device (handset) and switches off the acoustic input function. The detection function can be obtained by various and different magnetic sensors.
Prior art document US 2005/0117764 A1 discloses a hearing aid and an operating method for automatically switching to a telephone mode, wherein two hearing aids are considered in view of their levels of the input signals resulting from sounds or noise surrounding the user. The levels of both hearing aids are continuously compared, and when a difference between the levels detected exceeds a predetermined value, then it is assumed that at least in conjunction with one ear of the user, the handset of a telephone system is used, and an automatic switching to the telephone mode is performed. Specifically, at least one of the two hearing devices is switched to the telephone mode.
In general, when a handset of a telephone, whether a cordless telephone according to the DECT standard or a mobile telephone according to the GSM standard or according to some other standard is used, it is possible that when the telephone handset is placed close to the ear of a user wherein a hearing aid is placed and operated, a feedback effect occurs. This undesired feedback produces an unpleasing noise which makes the user feel uncomfortable. In some cases of the prior art mentioned above, the microphone function is completely switched off.